Gold-bearing tellurides loom large in the history of gold mining in Colorado. These mineral species are found in the San Juan Mountains, the La Plata Mountains, and at Cripple Creek. Other major localities in the United States include the huge gold fields of the Sierra Nevada foothills in California.

Gold-bearing tellurides are silvery to pyrite-yellow minerals, commonly striated, unlike gold which is a deeper yellow and rarely crystalline; and many of the lodes carrying gold-bearing tellurides were not discovered until the late 1800's. Placer gold was often found below the Cripple Creek Mine, but the lodes of the area were not recognized until the 1890's. Similar histories are common in other areas where gold-bearing tellurides were the major ore mineralogy. The miners of the 1860's would find gold placers below these vein deposits. However, the veins themselves were not recognized for what they were until some miner, perhaps cooking a meal on a camp fire surrounded by rocks, noticed gold appearing where a silvery, or pyrite-like mineral had been before.

This discovery led to a second gold rush to find these veins with a silvery to pyrite-like mineral, testing them with fire to determine if that mineral contained gold. Out of this rush came the mining camps of Cripple Creek and Telluride along with other mining camps in the San Juan region of Colorado. Of these, the mining camp of Cripple Creek is the most famous, producing nearly 20 million ounces of gold over a 70 year period from 1891 to 1961 (Smith, Raines, and Feitz, 1985). Additional gold was produced in the 1980's from heap leaching of low-grade gold-bearing mine tailings and ‘waste’ dumps.

A tip on finding tellurides: The mineral commonly has a greenish halo around it when weathered, due to oxidation of the telluride.

Gold-Bearing Telluride Mineralogy

Gold-bearing tellurides are common in gold-bearing deposits throughout the world. The following mineral species are the more common varieties. Localities listed are restricted primarily to the United States except when the mineral is not known to occur in this country.

Petzite: Ag3AuTe2 (silver-gold telluride)
Steel gray to black, metallic.
Gold Hill and Sunshine Mines in Colorado and various mines in Calaveras and Tuolumne Counties in California.

Dr. Eastman, who has a PhD in geology from Stanford University, has fifteen years experience in mining copper, uranium, silver, and gold, and most recently, eight years experience in groundwater resources and environmental consulting. He currently is a Project Manager in hydrogeology with Jehn Water Consultants, Inc. and Jehn Environmental, Inc., Denver, Colorado.